The broad goal of our research program is to understand the biological basis for language and other cognitive functions. In this project, Developmental Profile of Williams Syndrome Children, we address this important issue from a new perspective. Our studies under the Neurodevelopmental Research Center of adolescents with Williams Syndrome (WMS) point to a unique, behavioral profile in this rare metabolic disorder, in which there is a striking fractionation of higher cortical functions: linguistic abilities are selectively preserved in the face of severe general cognitive deficits. Our pilot studies of WMS younger children indicate a different cognitive phenotype showing extreme retardation in all developmental milestones, including language. Almost nothing is known about the initial capacity of WMS; we propose to investigate the development of language and cognition in WMS and matched Down Syndrome (DNS) children between 6 and 11 years of age, in order to provide critical tests of alternative theories of language, cognition and brain organization. Our specific aims include: The Decoupling of Language from Cognition in the Developing WMS Child. We examine language and cognitive correlates in the young child, to assess the hypothesis that particular linguistic abilities are dependent on the development of specific cognitive functions, or alternatively, that the two domains are dissociable in development. Differential Impairment of Components of Language. Syntactic functions in older WMS are remarkably spared, but semantic organization appears to be deviant; WMS show a proclivity for atypical words. We investigate the basis for this dissociation in the early stages of lexical and grammatical development in WMS. Dissociations Within Domains of Cognition. Even within the domain of spatial cognition, there are clusters of deficits and preservations which may be specific to WMS: markedly impaired visuospatial skills but a remarkable capacity for facial recognition as an island of sparing. WMS may result in selective attention to details of a configuration at the expense of a whole, while DNS results in an opposite profile, leading to hypotheses concerning the basis for the dissociation. Neural Substrate for WMS. These studies will be carried out in conjunction with Neurophysiological and Neuroanatomical studies of brain structure and function, to address specific hypotheses about the neural substrate for this unusual neuropsychological profile. These studies should contribute to our understanding of brain organization for language and cognitive functioning using a specific neurodevelopmental disorder as a model. WMS presents a rare dissociation of language from other cognitive capacities, providing an unusual opportunity to explore some of the central issues of developmental cognitive neuroscience.